1. Field of the Invention
The present invention relates to a control method for implementation in a power supply system and to a power supply system applying the same.
2. Description of the Related Art
Conventional electronic devices (such as computers, servers, etc.) receive electricity from a power supply that converts electricity from an external power source (such as commercial power), or receives electricity from power supply devices such as a battery, an uninterruptible power supply (UPS), etc. Conventionally, the electronic devices switch to using electricity from the power supply device when the external power source is cut-off. However, as soon as the external power source is cut-off, the power supply of the electronic device is required to continue providing electricity to the electronic device for a period of time before the power supply is able to switch to receiving electricity from the power supply device, ensuring a continuous supply of electricity to the electronic device. This period of time is referred to as a hold-up time in a hold-up operation that ensures continuous supply of electricity to the electronic device.
In the product specification of such electronic devices, a preferred hold-up time is usually specified (such as longer than 10 milliseconds). The hold-up time of a power supply is mainly related to a bulk capacitance of an output capacitor in the power supply, and is also affected by a load of the power supply. The actual bulk capacitance of the output capacitor of the power supply, when compared to a capacitance design value, usually has an error of +/−20%. Therefore, such error should be taken into account when designing the power supply in order to achieve a desired hold-up time. For instance, both a maximum error of the capacitance value of the output capacitor (such as −20%) and the type of the load electrically coupled with the power supply are taken into account in order to ensure that the hold-up time of the power supply satisfies a design requirement.
Although the above-mentioned hold-up time of the power supply may satisfy a design requirement, the actual hold-up time of each power supply and the actual bulk capacitance value of the output capacitor are not displayed. Therefore, this is disadvantageous for production management of the power supply during manufacturing, and it is inconvenient for a user to perform power management related to the power supply.
Moreover, the bulk capacitance of the output capacitor of the power supply usually decreases with time, and the rate of decrease may vary from one output capacitor to another, not to mention that the load electrically coupled with the power supply may also be modified or swapped. Additionally, it may also be difficult for a user to obtain the actual bulk capacitance of the output capacitor while the power supply is outputting electricity to the load. Thus, a hold-up time of the user's power supply may not be estimated, and this presents difficulties for the user to perform power management related to the power supply.